code: def test_monthly_data():
      """Tests monthly data with default template. This should raise an error."""
      df = pd.DataFrame(
          {
              "ts": pd.date_range("2020-01-01", freq="MS", periods=100),
              "y": 1,
          }
      )
      with pytest.raises(
          ValueError,
          match="The lag unit 'week' must be at least equal to the data frequency 'MS'.",
      ):
          forecaster = Forecaster()
          metadata_param = MetadataParam(
              time_col="ts", value_col="y", freq="MS"
          )
          evaluation = EvaluationPeriodParam(
              cv_max_splits=0, test_horizon=0
          )
          forecast_config = ForecastConfig(
              forecast_horizon=24,
              model_template=ModelTemplateEnum.LAG_BASED.name,
              metadata_param=metadata_param,
              evaluation_period_param=evaluation,
          )
          forecaster.run_forecast_config(df=df, config=forecast_config)
  
imports: import pandas
  import pytest
  from testfixtures import LogCapture
  from greykite.common.aggregation_function_enum import AggregationFunctionEnum
  from greykite.common.constants import LOGGER_NAME
  from greykite.common.constants import PREDICTED_COL
  from greykite.framework.templates.autogen.forecast_config import EvaluationPeriodParam
  from greykite.framework.templates.autogen.forecast_config import ForecastConfig
  from greykite.framework.templates.autogen.forecast_config import MetadataParam
  from greykite.framework.templates.autogen.forecast_config import ModelComponentsParam
  from greykite.framework.templates.forecaster import Forecaster
  from greykite.framework.templates.lag_based_template import LagBasedTemplate
  from greykite.framework.templates.model_templates import ModelTemplateEnum
  from greykite.framework.utils.result_summary import summarize_grid_search_results
  from greykite.sklearn.estimator.lag_based_estimator import LagBasedEstimator
  from greykite.sklearn.estimator.lag_based_estimator import LagUnitEnum
label_desc: Use image node_id 13 for calling a global function with example usage: test_monthly_data() without return types